Among the compounds which have pyridonecarboxylic acid as a basic skeleton, many are known to be useful as synthetic antibacterial agents due to their excellent antibacterial activities and a broad antibacterial spectrum. Mention may be given to norfloxacin (Japanese Patent Application Kokai No. 141286/1978), enoxacin (Japanese Patent Application Kokai No. 31042/1980), ofloxacin (Japanese Patent Application Kokai No. 46986/1982), cyprofloxacin (Japanese Patent Application Kokai No. 76667/1983) and the like, which have widely found a clinical utility as therapeutic agents for infectious diseases.
These compounds, however, are not sufficiently satisfactory in terms of antibacterial activities, intestinal tract absorption, metabolic stability, minimized adverse side effects, and the like, and hence novel compounds which meet these requirements have been desired.
Under the above circumstances, the present inventors have conducted careful studies with a view toward obtaining clinically excellent synthetic antibacterial agents, and have found that the compounds represented by formula (1) described hereinafter provide excellent oral absorption, exhibit excellent antibacterial activities against gram negative and gram positive bacteria and thus are very useful as synthetic antibacterial agents, leading to the completion of the invention.